Facile Electrochemical Route Research Articles

A string of nickel hexacyanoferrate nanocubes coaxially grown on a CNT@bipolar conducting polymer as a high-performance cathode material for sodium-ion batteries

The development of suitable cathode materials for sodium-ion batteries is the key issue to realize their large-scale applications owing to the lack of appropriate materials with adequate electrochemical capacity and reversibility for Na-ion insertion reaction. Here, a string of nickel hexacyanoferrate (NiHCF) nanocubes is coaxially grown on a CNT@bipolar conducting polymer (BCP) by a facile electrochemical route, and used as a high-performance cathode material for sodium-ion batteries. The obtained cathode shows a surprisingly high specific capacity of 194 mA h g-1 upon the initial discharge, a good cycling performance and excellent rate performance. It is considered that the unique nanostructure not only effectively facilitates the electrode/electrolyte interaction and the electronic and ionic transportation but also exerts a synergistic effect between the BCP and NiHCF nanocubes to trigger the kinetics of the electron and ion transport. It is expected that such a promising environmentally friendly alternative cathode material can be widely applied for sodium-ion batteries (SIBs).

Tuning of superhydrophobic to hydrophilic surface: A facile one step electrochemical approach

Tuning surface wettability is of great interest for both scientific research and practical applications. We report a facile electrochemical route for tuning the superhydrophobic surface of stearic acid (SA) modified copper with over-oxidized polypyrrole (OPPy). A systematic study was performed on the relationship between pyrrole concentrations and wetting states of SA modified copper surface. The wettability of the SA modified copper surface was monotonically converted from superhydrophobicity to hydrophilicity by increasing the pyrrole concentration during the process of electrochemical deposition.

Surfactant Effect in Polypyrrole and Polypyrrole with Multi Wall Carbon Nanotube Counter Electrodes: Improved Power Conversion Efficiency of Dye-Sensitized Solar Cell.

In our present study, polypyrrole-1 (PPy1), polypyrrole-2 (PPy2), and polypyrrole-2/multi wall carbon nanotube composite film (PPy2/MWCNT) were proposed as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs) to replace the precious Pt CE. These films were fabricated on fluorine-doped tin oxide substrates by using a facile electrochemical polymerization route, and served as CEs in DSSCs. It is shown that the introduction of anionic surfactant, sodium dodecyl sulfate (SDS), enhanced the catalytic activity, thus leading to an improvement in the performance of PPy2. Further, introduction of MWCNT resulted in increase in conversion efficiency of DSSCs with PPy2/MWCNT composite film. The Tafel and electrochemical impedance analysis revealed that the PPy2 and PPy2/MWCNT CEs prepared with anionic surfactant possessed more catalytic activity and lower charge transfer resistance in comparison with PPy1 -based CE. This resulted in a better conversion efficiency of 5.88% for PPy2/MWCNT-based DSSC under 1 sun condition, reaching 86% of the DSSC based on reference Pt counter electrode (6.86%). These results indicate that the composite film with high catalytic properties for I3- reduction can potentially be used as the CE in a high-performance DSSC.

Fabrication and electrochemical performance of nanoflake MnO2@carbon fiber coaxial nanocables for supercapacitors

Nanoflake MnO2@carbon fiber coaxial nanocables were fabricated by a facile electrochemical deposition-oxidation route. The morphology, structure, composition, and pseudocapacitive performance of the obtained composite material were evaluated by scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, cyclic voltammetry, and galvanostatic charge–discharge measurements. The results show that the nanoflake MnO2 on the carbon fibers is highly amorphous and hydrous. The nanostructured material shows nearly symmetrical and rectangular CV curves in the scan-rate range from 2 to 50 mV s−1. When used as electrodes for supercapacitors, the material shows a capacitance of 511.8 F g−1 at 1 A g−1 (based on the mass of MnO2), excellent high-rate capability, and cycling stability.

Polypyrrole and Polypyrrole-Multi Wall Carbon Nanotube for Alternative Counter Electrodes in Dye-sensitized Solar Cells

In our present study, the composite film of PPy/MWCNT (polypyrrole and multi-wall carbon nanotubes) and PPy were proposed as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs) to replace the precious Pt CE. The PPy and PPy/MWCNT composite films were fabricated on fluorine-doped tin oxide substrates by using a facile electrochemical polymerization route, and served as CEs in DSSCs. The electrochemical impedance spectroscopy and Tafel measurements revealed that the PPy/MWCNT CE possessed more excellent electrocatalytic activity and lower charge transfer resistance of 171.06 Ω in comparison with a PPy CE (338.6 Ω). The DSSC assembled with the PPy/MWCNT CE exhibited a better power conversion efficiency (PCE) of 4.17% under the illumination of 100 mW cm2, comparable to that of the DSSC based on reference Pt CE (6.86%). Compared with a DSSC using PPy CE with PCE of 3.45%, the PCE of DSSC using PPy/MWCNT CE was increased by 20%. Therefore, the PPy/MWCNT composite film can be considered as a promising alternative CE for DSSC due to its high electrocatalytic performance and excellent electrochemical stability.

Co(OH)2 @PANI Hybrid Nanosheets with 3D Networks as High-Performance Electrocatalysts for Hydrogen Evolution Reaction.

Hybrid electrocatalysts with excellent electrocatalytic activity for hydrogen reduction are fabricated using an efficient and facile electrochemical route. The electronic and synergistic effects between Co(OH)2 and polyaniline (PANI) in the composite structure are the key factors that generate the high electrocatalytic activity and excellent stability. A highly efficient, non-precious metal-based flexible electrocatalyst for high-performance electrocatalysts is shown, which reveals a novel route for the design and synthesis of electrocatalysts.

Electrochemical deposition of silver on manganese dioxide coated reduced graphene oxide for enhanced oxygen reduction reaction

We have prepared a reduced graphene oxide (rGO)-supported silver (Ag) and manganese dioxide (MnO2) deposited porous-like catalyst (denoted as rGO/MnO2/Ag) through a facile electrochemical deposition route and have been used as a cathode catalyst for oxygen reduction reaction (ORR) in alkaline fuel cells. The physical properties of rGO/MnO2/Ag have been investigated via several instrumental methods. This material exhibits a polycrystalline structure characterized by Ag/MnO2 microsphere formation as a result of Ostwald ripening. The X-ray diffraction and X-ray photoelectron spectroscopy data reveal that the MnO2 and Ag have been slightly alloyed and Mn presents with the dioxide form on rGO. The electrochemical properties of the electrocatalyst have been studied via several voltammetric methods. The results demonstrated that the rGO/MnO2/Ag has an excellent catalytic activity for ORR in alkaline media compared to the other tested electrodes. Particularly, it shows 1.2 times higher current density and better electron transfer rate at 0.3 V per O2 than that of 20 wt% Pt/C. The other kinetic analysis reveals that the O2 has reduced directly to H2O through a nearly four-electron pathway with better anodic fuel tolerance and duration performance than that of 20% Pt/C.

Transformation of ZnO nanorods into nanotubes and their field emission studies

Synthesis of vertically well-aligned ZnO nanorods on Au coated silicon substrate by a facile electrochemical route has been carried out. The transformation of as-deposited ZnO nanorods into nanotubes was achieved via simple, single step, chemical etching process using KOH as etchant. The influence of various parameters of the etching, such as concentration of the etchant, bath temperature and duration on morphological features of the ZnO nanotubes has been investigated. It is observed that formation of ZnO nanotubes with smooth inner and outer surfaces is achieved when the etching was performed at 65°C for 1 h duration, and at higher bath temperatures and longer durations, over etching of nanorods takes place. Field emission investigations of the ZnO nanorods and nanotubes were carried out at base pressure of 1 × 10-8 mbar. The values of turn-on field, corresponding to emission current density of 1 μA/cm2 were observed to be 7.2 V/μm and 8.4 V/μm, corresponding to ZnO nanorods and nanotubes emitter respectively, and emission current density of ~ 352.5 μA/cm2 has been drawn from the ZnO nanotubes emitter at an applied field of 13.77 V/μm. The ZnO nanotubes emitter exhibits excellent emission current stability at the preset value of 1 μA over duration of 3 h, indicating its potential as electron source for practical applications.

Polypyrrole nanostructures and their field emission investigations

Polypyrrole (PPy) nanostructures have been synthesized on indium doped tin oxide (ITO) substrates by a facile electrochemical route employing cyclic voltammetry (CV) mode. The morphology of the PPy thin films was observed to be influenced by the monomer concentration. Furthermore, FTIR revealed formation of electrically conducting state of PPy. Field emission investigations of the PPy nanostructures were carried out at base pressure of 1×10-8 mbar . The values of turn-on field, corresponding to emission current density of 1 μA/cm2 were observed to be 0.6, 1.0 and 1.2 V/μm for the PPy films characterized with rod-like, cauliflower and granular morphology, respectively. In case of PPy nanorods maximum current density of 1.2 mA/cm2 has been drawn at electric field of 1 V/μm. The low turn on field, extraction of very high emission current density at relatively lower applied field and good emission stability propose the PPy nanorods as a promising material for field emission based devices.

Mechanical properties of the poly(vinyl alcohol) based nanocomposites at low content of surfactant wrapped graphene sheets

One necessary point towards achieving the enhanced mechanical properties in the nanocomposite systems, comprising a polymeric matrix and the graphene sheets (GSs) as the reinforcement, is the number of GSs layers regarding its relation with the gyration radius of the matrix. In this study, a stable suspension containing the surfactant wrapped graphene sheets (SWGSs) was successfully synthesized via a facile electrochemical route in the sodium dodecyl sulfate media. The effect of the applied potential was qualified and quantified during preparation of SWGSs by employing X-ray diffraction, chronoamperometry and Raman spectroscopy. It was found that an increase in the level of applied potential from 5 to 15 V improves the production yield of SWGSs (≈56%). The prepared SWGSs, which contained monolayer as well as multilayer sheets, were then dispersed in the Poly(Vinyl Alcohol) (PVA) matrix through liquid blending method. It was observed that the tensile strength and Young's modulus of the fabricated nanocomposite (PVA/SWGSs) increase even at low level GSs content. Furthermore, the effect of temperature on the fabrication process of the nanocomposites was evaluated via thermal analysis.

One-step electrochemical synthesis of Bi3.84W0.16O6.24 with superior photocatalytic activities

Bi3.84W0.16O6.24 nanoparticles were successfully prepared by a facile electrochemical route at room temperature in just 10 minutes.

A Perovskite-Type Lanthanum Cobaltite Thin Film Synthesized via an Electrochemical Route and Its Application in SOFC Interconnects

Metal oxides with a perovskite structure have attracted great interest in a wide range of technical applications, including solid oxide fuel cells (SOFCs), owing to their unique electronic, chemical, and structural features. Recently, significant efforts have been put into developing simple and cost-effective methodologies to controllably produce perovskite oxide layers for SOFC applications. In this study, we demonstrate the fabrication of a perovskite-type lanthanum cobaltite (LaCoO3) film via a facile electrochemical route and its feasibility as a conductive coating for metallic interconnects in SOFCs. A uniform, dense, and adhesive LaCoO3 film with a thickness of about 1 μm (mixed with a small amount of Co3O4) is formed on a cobalt-coated stainless steel substrate through an electrodeposition process involving nitrate reduction and hydroxide precipitation, followed by thermal conversion in air. The fabricated perovskite film serves as an efficient conductive coating that can mitigate degradation in the electrical properties of metallic interconnects under typical SOFC operating conditions.

A facile electrochemical route to the preparation of uniform and monoatomic copper shells for gold nanoparticles.

Copper on gold forms a monolayer deposit via underpotential deposition. For gold particles adsorbed at a liquid-liquid interface this results in a uniform one monolayer thick shell. This approach offers a new route for the uniform functionalisation of nanoparticles and presents a way to probe fundamental processes that underlie nanoparticle synthesis.

A novel codoping approach for enhancing the performance of polypyrrole cathode in a bioelectric battery

A conducting polymer (CP) based bioelectric battery provides a promising alternative to commercial lithium batteries to drive biomedical devices. However, the low power density limits practical application. Here, we synthesize a polypyrrole (PPy)/anthraquinone sulfonate (AQS)/reduced graphene oxide (r-GO) composite via a facile electrochemical route, and use this as a novel cathode material for bioelectric batteries. The presence of r-GO significantly enhanced the electrochemical properties of PPy and led to greatly improved cell performance compared to that of PPy/AQS. The resultant PPy/AQS/r-GO composite delivered a maximum power density of 6240.5mWm−2, 14.2 times higher than that of PPy/p-toluenesulfonate (pTS) as reported previously.

Enhanced Capacity of Polypyrrole/Anthraquinone Sulfonate/Graphene Composite as Cathode in Lithium Batteries

A facile electrochemical route was applied to prepare polypyrrole (PPy)/anthraquinone sulfonate (AQS)/reduced graphene oxide (r-GO) composite. The as-synthesized composite showed an interconnected porous structure, which is related to the competitive relationship between two dopants. The cyclic voltammograms and electrochemical impedance spectra confirmed that the presence of highly conductive r-GO in PPy matrix ensured an efficient redox reaction obtained for redox-active AQS. As a result, the PPy/AQS/r-GO composite exhibited an enhanced specific capacity of 127.2 mAh g−1 with ca. 100% coulombic efficiency at 0.1 A g−1. Furthermore, the superior rate capability and cycling stability were also observed for PPy/AQS/r-GO, compared to AQS doped PPy. It is possible to adopt this co-dopants system for creating electro-active polymer materials with high capacities that are comparable to that of conventional inorganic intercalation electrode materials.

Fabrication of high performance multi-walled carbon nanotubes/polypyrrole counter electrode for dye-sensitized solar cells

In our present study, the composite film of MWCNTs/Ppy (multi-walled carbon nanotubes and polypyrrole) was proposed as CE (counter electrode) catalyst in DSSCs (dye-sensitized solar cells) to speed up the reduction of triiodide to iodide. The MWCNTs/Ppy composite film was synthesized and fabricated it on rigid fluorine-doped tin oxide substrates by using a facile electrochemical polymerization route, and served as CE in DSSCs. The unique structural characteristics including rough surface consisted of the numerous MWCNTs coated on Ppy nanoparticles guaranteed fast mass transport for the electrolyte, and enabled the MWCNTs/Ppy CE to speed up the reduction of triiodide to iodide. The electrochemical analyses came from cyclic voltammetry and electrochemical impedance spectroscopy revealed that the MWCNTs/Ppy CE possessed more excellent electrocatalytic activity, electrochemical stability and lower charge transfer resistance of 2.82 Ω cm2 in comparison with a sputtered-Pt CE. The DSSC assembled with the novel MWCNTs/Ppy CE exhibited a high light-electric conversion efficiency of 7.42% under the illumination of 100 mW cm−2, comparable to that of the DSSC based on sputtered-Pt electrode (6.85%). Therefore, the MWCNTs/Ppy composite film can be considered as a promising alternative CE for DSSC due to its high electrocatalytic performance and excellent electrochemical stability.

Versatile Ag dendrites: simple galvanostatic deposition and applications

Large Ag dendrites were rapidly deposited via a facile electrochemical route at a deposition current of 20 mA for 10 min in air at room temperature, employing a mixed system of AgNO3 and NH3·H2O as the electrolyte. The phase and morphology of the as-prepared product were characterized by means of powder X-ray diffraction (XRD), energy dispersive spectrometry (EDS), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and scanning electron microscopy (SEM). It was found that the original ammonia amount played a crucial role in the formation of Ag dendrites. Experiments showed that the as-deposited Ag dendrites exhibited versatile applications in some fields including super-SERS performance for the detection of rhodamine-6G, highly effective antimicrobial activities toward Escherichia coli and excellent catalytic capacities for the reduction of 4-nitrophenol to 4-aminophenol.

Electrochemical deposition of Al-doped ZnO transparent conducting nanowire arrays for thin-film solar cell electrodes

This paper reports a facile electrochemical route for growing Al-doped ZnO transparent conducting nanowire (NW) arrays on fluorine-doped tin oxide (FTO) substrates. The effects of precursor concentration, Al/Zn ratio, and applied potential on the morphologies, electrical conducting, and optical transmittance properties are examined. The Al-doped ZnO NWs are well-aligned with the c-axis being perpendicular to the substrates. Moreover, the Al-doped ZnO NW arrays, which had been thermally treated at 420°C in vacuum, exhibit good conductivity with the minimum sheet resistance of 162Ω/sq and light scattering effect. This initiates a new method for growing large area doped ZnO transparent conducting films with light scattering at low cost, which is expected to be used for the transparent electrodes of thin-film solar cells.

Electrochemical route to the synthesis of ZnO microstructures: its nestlike structure and holding of Ag particles

A simple and facile electrochemical route was developed for the shape-selective synthesis of large-scaled series of ZnO microstructures, including petal, flower, sphere, nest and clew aggregates of ZnO laminas at room temperature. This route is based on sodium citrate-directed crystallization. In the system, sodium citrate can greatly promote ZnO to nucleate and directly grow by selectively capping the specific ZnO facets because of its excellent adsorption ability. The morphology of ZnO is tuned by readily adjusting the concentration of sodium citrate and the electrodeposition time. Among the series structures, the remarkable ZnO nestlike structure can be used as a container to hold not only the interlaced ZnO laminas but also Ag nanoparticles in the center. The special heterostructures of nestlike ZnO holding Ag nanoparticles were found to display the superior properties on the surface-enhanced Raman scattering. This work has signified an important methodology to produce a wide assortment of desired microstructures of ZnO.PACS81 Materials science 81.07.-b nanoscale materials and structures Fabrication Characterization 81.15.-z Methods of deposition of films Coatings Film growth and epitaxy.

Growth of Polypyrrole–Horseradish Peroxidase Microstructures for $\hbox{H}_{2}\hbox{O}_{2}$ Biosensor

Conducting polymer microstructures for enzymatic biosensors are developed by a facile electrochemical route. Horseradish peroxide (HRP)-entrapped polypyrrole (PPy) films with bowl-shaped microstructures are developed on stainless steel (SS 304) substrates by a single-step process. Potentiodynamic scanning/cyclic voltammetry is used for generation of PPy microstructures using electrogenerated oxygen bubbles stabilized by zwitterionic surfactant/buffer N-2-hydroxyethylpiperazine N-2-ethanesulfonic acid as soft templates. Scanning electron microscopic images reveal the bowl-shaped structures surrounded by cauliflower-like fractal PPy films and globular nanostructures. Raman spectroscopy reveals the oxidized nature of the film. Sensing properties of PPy-HRP films for hydrogen peroxide (H2O2) are demonstrated. Electrochemical characterization of the sensor films is done by linear sweep voltammetry (LSV) and amperometry. LSV results indicated the reduction of H2O2 and linearity in response of the sensing film. The amperometric biosensor has a performance comparable to those in the literature with advantages of hard-template free synthesis procedure and a satisfactory sensitivity value of 12.8 μA/(cm2·mM) in the range of 1-10 mM H2O2.